GM releases 3-valve per cylinder pushrod engine.
Displacement: 6.3L
2 intake valves
1 exhaust valve
Power: 470hp @ 6700rpm
Torque: 385ft-lb @ 5600rpm.
This engine was originally slated for the C6 Z06 but the 2V 7.0L was used instead. Basically it's a standard pushrod V8 with 16 pushrods operating 1 exhaust valve and 2 intake valves per cylinder. Here's a tech article from January 2004 that explains most of the workings of the 3V pushrod engine: Link
QUOTE
First, the reasoning for the changes are as follows.
Adding a second intake valve improves intake air flow, which provides some value, but perhaps more importantly the design relocates the exhaust valve and the spark plug within the combustion chamber. The exhaust valve moves from alongside the intake valve to the other side of the cylinder, so less exhaust heat transfers to the intake port. The resulting cooler intake charge boosts power and efficiency. Positioning intake and exhaust valves on opposite sides of the combustion chamber leaves space in the center for the spark plug, which improves combustion efficiency. Together, these improvements boost power output by 10-15%.
The three-valve engine has the intake valves in a straight line, operating them with a forked rocker arm off a conventional rocker shaft. The solution is a pair of rocker arms. One mounts on the rocker shaft where the exhaust rocker arm would be on a two-valve engine. Instead of acting on the valve, however, the first rocker pushes on a short, nearly horizontal pushrod that runs across the head to a freestanding stud-mounted rocker arm. A short, nearly horizontal pushrod links the intermediate rocker arm located on the conventional rocker shaft to the stud-mounted rocker that opens the exhaust valve. A forked rocker arm operates both intake valves. This second rocker arm pivots the movement into the right direction for the exhaust valve.
The three-valve heads are about 1 in (25 mm) wider than the two-valve heads, but they maintain the low profile that is an advantage of OHV engines. The new heads will work with the displacement-on-demand (DOD) cylinder-deactivation system that will arrive on the two-valve Generation IV engine.
Adding a second intake valve improves intake air flow, which provides some value, but perhaps more importantly the design relocates the exhaust valve and the spark plug within the combustion chamber. The exhaust valve moves from alongside the intake valve to the other side of the cylinder, so less exhaust heat transfers to the intake port. The resulting cooler intake charge boosts power and efficiency. Positioning intake and exhaust valves on opposite sides of the combustion chamber leaves space in the center for the spark plug, which improves combustion efficiency. Together, these improvements boost power output by 10-15%.
The three-valve engine has the intake valves in a straight line, operating them with a forked rocker arm off a conventional rocker shaft. The solution is a pair of rocker arms. One mounts on the rocker shaft where the exhaust rocker arm would be on a two-valve engine. Instead of acting on the valve, however, the first rocker pushes on a short, nearly horizontal pushrod that runs across the head to a freestanding stud-mounted rocker arm. A short, nearly horizontal pushrod links the intermediate rocker arm located on the conventional rocker shaft to the stud-mounted rocker that opens the exhaust valve. A forked rocker arm operates both intake valves. This second rocker arm pivots the movement into the right direction for the exhaust valve.
The three-valve heads are about 1 in (25 mm) wider than the two-valve heads, but they maintain the low profile that is an advantage of OHV engines. The new heads will work with the displacement-on-demand (DOD) cylinder-deactivation system that will arrive on the two-valve Generation IV engine.
Bottomline: With displacement-on-demand, cam-phasing variable valve timing and the 3V heads, this engine lineup will be competitive with the best of the overhead cam engines in power delivery while still retaining the compact and lightweight advantages of the pushrod engine. Plus it's GM high-performance so you know it'll be affordable.
And I need to go clean my pants.
